This invention relates to a joint assembly and a method for making a joint assembly, and more particularly to a telescoping joint assembly and a method for making a telescoping joint assembly having a pair of members which telescopingly cooperate to form a relatively tight and reliable joint.
Automotive vehicles and other types of assemblies often utilize telescoping type joints and/or joint assemblies to operatively couple selectively rotatable shafts or members in a manner which allows torque or rotational energy to be communicated and/or transmitted by and between the coupled members, while concomitantly allowing the coupled members to independently move axially with respect to each other (e.g., to selectively move xe2x80x9ctoward and awayxe2x80x9d from each other).
For example and without limitation, a vehicle steering system or assembly generally includes a steering shaft or column and a telescoping intermediate shaft which is coupled to and transfers torque between a steering column and a steering gear assembly. Particularly, the rotational energy of the steering column is transferred through the telescoping intermediate shaft to the gear assembly and the wheel suspension assembly, thereby allowing the vehicle to be selectively steered.
Typically, the intermediate shaft comprises and/or includes an inner shaft or member and an outer shaft or member which movably and selectively receives and/or xe2x80x9cmatesxe2x80x9d with the inner shaft or member and which cooperates with the inner member to allow the steering column and gear shaft to be xe2x80x9caxially compliantxe2x80x9d (i.e., to selectively and independently move xe2x80x9ctoward and awayxe2x80x9d from each other).
In order to substantially reduce friction and improve the performance, compliance, and efficiency of this intermediate shaft and/or steering shaft assembly (as well as other types of joint assemblies), the inner member is typically coated or lined with a resin, rubber or polymer material, or contains a bearing assembly. The telescoping intermediate shaft compensates for the relative movement between the vehicle body and vehicle frame which occurs as the car is driven and allows at least one of the coupled members, such as the steering column, to substantially and desirably xe2x80x9ccollapsexe2x80x9d in the event of a collision or accident, thereby substantially reducing the probability of injury to the driver. The telescoping shaft may further allow the steering column to be adjusted by the driver in an axial or telescopic manner.
Although this intermediate shaft, as well as other substantially similar types of prior joint assemblies, effectively transmit torque between a pair of coupled members or shafts while concomitantly allowing the coupled members to be axially compliant, they suffer from some drawbacks.
For example and without limitation, these prior joint assemblies are typically relatively loose fitting and do not have a relatively precise fit or xe2x80x9ccorrespondencexe2x80x9d between the telescoping members and/or between one or more of the telescoping members and the liner or bearing assembly. Particularly, because the members and the liner/bearing assembly are each formed by separate and independent processes, the manufacturing xe2x80x9ctolerancexe2x80x9d associated with each of the members and the liner/bearing assembly are additively accumulated or xe2x80x9cstackedxe2x80x9d, thereby resulting in a relatively xe2x80x9cloosexe2x80x9d overall tolerance and a relatively imprecise or relatively loose fit. As a result, these prior telescoping joint assemblies suffer from undesirable xe2x80x9cslopxe2x80x9d, xe2x80x9clashxe2x80x9d, vibration, frictional loss, and/or xe2x80x9cfrictional lock-upxe2x80x9d, which require relatively costly and complicated modifications.
Particularly, these undesirable attributes hinder and/or undesirably diminish the sliding engagement between the telescoping members, resulting in an inefficient transmission of torque or rotational energy while concomitantly creating excessive wear and fatigue to and of the telescoping members, thereby causing failure and/or diminished performance (e.g., undesirably allowing vibrational forces and/or other movements/forces to be readily transferred between the coupled components and/or members, such as between the wheel suspension assembly and the steering column).
Efforts to improve these relatively loose joints typically include but are not limited to relatively costly sizing, adjusting, or machining of the respective shafts. Furthermore, in order to obtain a more precise tolerance or fit between the inner and outer members, the members must typically undergo relatively complex and undesirable machining processes after they have been formed and/or after a lining has been applied to the inner and/or outer member. This xe2x80x9cpost-fabricationxe2x80x9d machining undesirably increases the expense, time, and difficulty of the manufacturing process.
There is therefore a need to provide a telescoping joint assembly for coupling two members or shafts which overcomes at least some of the various and previously delineated drawbacks of prior coupling assemblies; which allows torque and rotational energy to be relatively efficiently transmitted between the two coupled members or shafts, while concomitantly allowing each of the members or shafts to be axially compliant; which provides for a substantially xe2x80x9ctightxe2x80x9d fit between the telescoping members; which substantially eliminates and/or reduces xe2x80x9cslopxe2x80x9d, lash, frictional loss, and/or xe2x80x9cfrictional lock-upxe2x80x9d; and which substantially eliminates the need for post-fabrication xe2x80x9cmachiningxe2x80x9d of the telescoping members.
It is a first object of the invention to provide a telescoping joint assembly and a method for making a telescoping joint assembly which overcomes some or all of the previously delineated drawbacks of prior telescoping joint assemblies.
It is a second object of the invention to provide a telescoping joint assembly which selectively allows torque and/or rotational energy to be transmitted and/or communicated between two telescoping members, while concomitantly allowing the telescoping members to selectively, independently, and reciprocally move toward and away from each other.
It is a third object of the present invention to provide a telescoping joint assembly which provides for substantially xe2x80x9ctightxe2x80x9d or precise dimensional fit or correspondence between two operatively assembled telescoping members.
It is a fourth object of the present invention to provide a telescoping joint assembly which substantially eliminates and/or reduces xe2x80x9cslopxe2x80x9d, xe2x80x9clashxe2x80x9d, frictional losses and/or xe2x80x9cfrictional lock-upxe2x80x9d, and which substantially eliminates and/or reduces the amount of vibrational forces transferred between the coupled members.
According to a first aspect of the present invention, a telescoping joint assembly is provided. The telescoping joint assembly includes a first member having an inner cavity; a second member which is selectively and movably disposed within the cavity and which cooperates with the first member to form a gap; a certain amount of a thermoplastic material which is disposed within the gap and which selectively shrinks and solidifies, thereby bonding to the second member and allowing the second member to be slidably disposed within the cavity.
According to a second aspect of the present invention a method for making a telescoping joint assembly is provided. The method includes the steps of providing a first member having a cavity of a first shape; providing a second member adapted to be inserted within the cavity; placing an amount of thermoplastic material within the cavity; heating the cavity effective to liquefy the thermoplastic material; heating the second member; inserting the heated second member within the cavity, effective to cause the thermoplastic material to be distributed within the cavity and around the second member; cooling the first member effective to solidify the material, thereby bonding the material onto the second member and creating a telescoping joint assembly.
These and other objects, aspects, features, and advantages of the present invention will become apparent from a consideration of the following specification and the attached drawings.